Characteristics of optical crystals

Common optical crystals have unique optical properties and are widely used in lasers, nonlinear optics and optical devices.Crystals used to make optical materials typically have the following characteristics:

High transmittance: there is a high light transmittance in a specific wavelength range, such as fluorite (CaF₂) has a high transmittance in the ultraviolet, visible and infrared band spectral region, which can make the light pass efficiently, thus ensuring the performance of the optical system.
Low absorption coefficient: The absorption of light is less, which can reduce the energy loss of light in the propagation process, like BBO crystal has a very low absorption coefficient, which is conducive to improving the stability of laser output power.
Suitable refractive index: It has a refractive index that meets the application needs, so as to effectively control the refraction and focusing of light, such as optical glass BK7, the refractive index is more moderate in the visible light range, and can be used to manufacture a variety of optical components.
Good dispersion characteristics: Some crystals, such as fluorite, have very small dispersion, which means that when different wavelengths of light propagate in it, the speed difference is small, which can reduce optical aberrations such as color difference and improve imaging quality.
Chemical stability: It is not easy to react with the surrounding chemical substances, has good corrosion resistance, and can maintain its performance stability under various environmental conditions, such as quartz (SiO₂) has good chemical stability, and can be used in a variety of chemical environments.
High hardness: Crystals with high hardness can resist scratching and wear, maintain the optical surface finish, such as sapphire (Al₂O₃) high hardness, wear resistance, often used to manufacture optical components that require high durability, such as high-end watch mirrors, optical Windows in the aerospace field.
High thermal stability: within a certain temperature range, the optical and physical properties of the crystal can remain stable, and will not change significantly due to temperature changes, such as bismuth silicate (BSO) crystals have good thermal stability, and can play its optical functions stably at different operating temperatures.

Good mechanical properties: with a certain strength and toughness, it can withstand the processing stress in the manufacturing process of optical components and the external force in actual use, and is not easy to break or damage to ensure the integrity and reliability of optical components.